Essentially there are two known methods of manufacturing an electrode for an alkaline storage cell.
The first method consists in directly preparing the active material in a suitable granular form and in inserting it in tubes or pockets of perforated metal sheet which serves as a current collector.
In some applications that require very rapid discharging, electrodes obtained by this method do not have adequate electrical characteristics since they do not include a conductive network inside the active material itself.
The second method avoids this drawback since it consists in inserting the active material in a "metal sponge" made from a sintered support. To do this, the support is made first from a strip (which may optionally be perforated) of metal ribbon or foil coated with a layer of very fine metal powder. The metal may be nickel, iron, etc . . . . The coated strip is passed through a sintering furnace at high temperature (about 1000.degree. C.) in the presence of inert or reducing gases in order to surface weld the grains of the metal powder to one another and to the strip.
Alternatively, the strip may be preheated and then passed for a period of a few seconds through a furnace fitted with high frequency (300 KHz to 600 KHz) or medium frequency (1 KHz to 10 KHz) generators.
The resulting sintered sponge (to provide the electrode with good conductivity characteristics) is impregnated with metal salts suitable for the type of electrode in question: for example, nickel or cadmium nitrates, chlorides or sulfates. These salts are treated chemically to precipitate inside the sintered support in the form of nickel hydroxide, cadmium hydroxide, etc . . . . It is then necessary to eliminate, by chemical or by electrochemical means, the unwanted residual salts. After all these operations, an electrode is obtained which is composed of a sintered metal support with active material in the discharged state integrated into the pores thereof. It is clear that to arrive at this result, it is necessary to make use of complex and expensive equipment and to expend large amounts of energy.
Preferred implementations of the present invention provide a simplified method requiring less manufacturing equipment.